A known apparatus for use in inflating a vehicle occupant restraint, such as an air bag, includes a container containing inflation fluid under pressure. A body of ignitable material is disposed within the container. An igniter assembly is actuatable to ignite the body of ignitable material. As the ignitable material burns, it heats the inflation fluid in the container to increase the fluid pressure in the container.
Typically, the container defines a generally cylindrical chamber. The chamber is filled with inflation fluid under pressure which is introduced into the chamber through a passage. Once the chamber has been filled with inflation fluid at a desired pressure, the passage is closed. The container includes a burst disk which is ruptured in response to vehicle deceleration of a magnitude indicating the occurrence of a collision. When the burst disk is ruptured, it defines an outlet opening through which the inflation fluid flows from the chamber of the container toward the air bag to inflate the air bag.